This invention is directed toward the field of subminiature compressional wave transducers and is more particularly directed to a transducer utilizing the electret principle of operation and to a method of fabricating such a transducer.
The prior art with which our invention is concerned arises from the well known condenser microphone type of transducer and has evolved from the discovery of the electret principle in its application to such general types of microphones and transducers.
The prior art contains numerous patents and publications relating to various forms of electret compressional wave transducers that have arrived and departed from the commercial scene. Some of these have been directed toward miniature and subminiature forms which are typically used in connection with hearing aids and the like. Whether large or small, the properties of an electret form of compressional wave transducers have proven desirable in many applications. While the superior performance of the electret form of transducer has long been recognized, its wide scale adoption has not been obtained, principally for the reasons of a decided lack of cost effectiveness. Some of the relatively high production cost have resulted from complicated structures and others have resulted from the use of manufacturing methods and techniques which may result in an undesired low percentage of acceptable products when presented in their final assembled presumably operable condition.